The invention relates generally to a method for preserving data through a boot process. In particular, the invention relates to a method for preserving data generated by a startup program for access by a run-time program after a softboot process.
In some applications, processors are used to execute different programs resident in different memory units. For example, a processor can be used to execute a startup program in read-only memory (ROM) and then execute a run-time program downloaded from an external device. This requires establishing a communications channel between the processor and the external device during execution of the startup program prior to downloading the run-time program from the external device.
Typically, the program in ROM closes the communication channel before transferring control to the downloaded run-time program. As a result, the state of the communication channel is cleared and the downloaded application establishes a new communications channel, unfortunately, opening the new communications channel adds more time to the extended time required to download the run-time program. Thus, it would be advantageous to preserve the communications channel while executing the startup program and then access it during execution of the run-time program.
The invention relates to a method for preserving data through a softboot process. A first program (e.g., a boot program in ROM) opens a communication channel between a processor and an external module. Pointers identify reserved areas in dynamic random-access memory (DRAM) where data to be passed to a run-time program, such as communication state variables and self-test data, are written. The run-time program is downloaded to a different area in DRAM so that the data to be passed is preserved and can be retrieved during execution of the run-time program.
In one aspect, the method includes the steps of executing a startup program in a processor, establishing a communications channel between the processor and an external module, and storing a data set in a first predetermined area of a local memory module. In one embodiment, the communications channel is established between the processor and a memory module in the external module. The method includes the additional steps of downloading a run-time program from the external module into a second predetermined area of the local memory module and executing the run-time program in the processor, including accessing the communications channel data set.
In one embodiment, the method includes the step of storing self-test data in the local memory module. In another embodiment, the self-test data is stored in a third predetermined area of the local memory module.
In one embodiment, the method includes the step of verifying proper downloading of the run-time program. In another embodiment, the step of verifying proper downloading includes examining a checksum in the run-time program.